Cortical spreading depression reduces paraventricular activation induced by hippocampal neostigmine injection

The firing rate of the neurons of the hypothalamic paraventricular nucleus, the temperatures of the interscapular brown adipose tissue and of the colo n (T-IBAT and T-c) were monitored in 24 urethane-anesthetized male Sprague- Dawley rats divided into four groups. These variables were measured before and after hippocampal injection of neostigmine (5 x 10(-7) mol) in the 1st and 2nd groups or of saline in the 3rd and 4th groups. The hippocampal inje ction was preceded by cortical spreading depression in the Ist and 3rd grou ps, while the cortical depression was not induced in the 2nd and 4th groups . The results show an increase of firing rate, T-IBAT and T-c after neostig mine injection in the rats without cortical depression. Cortical spreading depression significantly reduces these enhancements. These findings demonst rate that: (1) the paraventricular nucleus plays a significant role in the hyperthermia induced by neostigmine injection into the hippocampus; and (2) the cerebral cortex is involved in the control of the paraventricular acti vity. (C) 1999 Published by Elsevier Science B.V. All rights reserved.